Unpack the X source, then put all of these in debian/patches, and remove
310_arm_compiler_h.diff from that directory. It should build, and if
all goes well, it may even work!

The first two are based on the previous 310_arm_compiler_h.diff and 600
and 600a from debian/held-patches. No rocket science here, I just had
to tweak it a bit to use the inx/outx prototypes from libc, specifically
sys/io.h. The last two differ from what's there now only in line
numbers so their compiler.h hunks are applied without offset.

Do you know if these patches could help makeing the m68k elfloader work?

I don't think so, I think there's quite a bit of ARM-specific stuff in
there. But you can change some of the #ifdef(__arm__) to use m68k as
well, and give it a shot!